1. Field of the Invention
The present invention relates to an inorganic scintillator.
2. Related Background Art
In the positron emission computed tomography (hereinafter referred to as “PET”), optical characteristics (wavelength conversion characteristics, etc.) of scintillators employed therein greatly influence imaging performances of the whole system, whereby an improvement in the optical characteristics of scintillators is one of the most important points in ameliorating the imaging performances of the whole system. Therefore, searches for scintillator materials which can construct scintillators having excellent optical characteristics, and developments for manufacturing techniques such as crystal growing techniques for putting these scintillators into practical use have vigorously been under way. In the field of high-energy physics, on the other hand, there have been demands for practically using scintillators which can efficiently detect a minute amount of high-energy particles in order to detect those flying from the space to the earth and using them in experiments for analysis or the like.
As scintillators employed in the PET, those with a high fluorescence output, those with a short fluorescence decay time, those with a high energy resolution, etc. have been in demand. In particular, from the viewpoint of alleviating the burden on a sample to be inspected by using the PET, it is necessary to shorten the inspection time per sample, which requires scintillators with a short fluorescence decay time.
Known as examples of scintillators aimed at shortening the fluorescence decay time are inorganic scintillators configured such that cerium is included as a luminescence center in a matrix material made of a mixed metal oxide containing lanthanoid (see, for example, Japanese Patent Publication No. SHO 62-8472). Examples of these inorganic scintillators include those having a chemical composition represented by the general formula of CeαLn2-αSiO5 or the general formula of CeβLn2-βAlO3. Here, 0<α<0.1; 0<β<0.1; and Ln is Sc, Y, La, Gd, or Lu.